It is well known that actuators normally have moving parts, which with their movement, determine the operation of mechanical devices such as levers, gears, cams or whatsoever. The movement of the actuator is usually given by an elongated element which is moved axially. For example, the elongated element can be a rod which is the stem of an electro-mechanical or hydraulic piston that moves within a corresponding cylinder.
One of the most important problems in these types of actuators is the sealing between the fixed part (the cylinder) and mobile one (the rod). Indeed, in humid environments, such as, for example, marine environments, where the actuators are immersed in water, it is possible that in the gaps inevitably present between the two parts named above, moisture and/or impurities can penetrate which damage, often in a short time, the operation of the actuator. Attempts have been made, to remedy that problem by covering both parts with a bellows. However, these do not prevent the entering of water and do not adequately protect the piston rod so that the problem is not suitably resolved.